1. Field of the Invention
This invention relates to an automatic microfilm retrieval system which makes use of a microfilm bearing contents of a dictionary or the like recorded thereon and which can automatically retrieve a film portion bearing an index word in response to an input signal obtained by depressing keys.
2. Description of the Prior Art
Heretofore it has been the common practice to record an English-Japanese dictionary, for example, on a microfilm in a reduced scale, automatically retrieve a microfilm portion bearing a desired index word by depressing keys corresponding to such index word and project the retrieved microfilm portion on a screen in an enlarged scale. In this case, it is important to carry out successive steps of depressing the keys corresponding to the desired index word and retrieving the film portion bearing the index word in a rapid and reliable manner with the aid of a device which is simple in construction.
In the conventional microfilm retrieval system, in order to obtain a signal for retrieving a film portion, a signal representing the relation between an index word and a microfilm portion bearing the index word recorded thereon must be stored beforehand in a memory. This signal thus stored in the memory causes the index word corresponding to the depressed keys to convert into a signal corresponding to the microfilm portion bearing the index word and this signal is used for retrieving the microfilm.
In such conventional system, it is indispensable to use the memory, so that the system becomes complex in construction and very troublesome in operation of storing beforehand the above mentioned signal in the memory, that the system is constructed such that at first the input signal produced by depressing the keys is converted into a position representing signal and then the signal thus converted is used to retrieve the information on the microfilm, thereby limiting the retrieving speed, and that, in the case of replacing the existing microfilm by another kind of microfilm, provision must be made of a memory corresponding to such microfilm.